Insecure object reference - Files

Need

Secure and validate object references to prevent unauthorized access to files

Context

• Usage of Go 1.16 for building efficient and scalable applications
• Usage of gin-gonic/gin for building web applications and APIs in Go
• Usage of net/http for creating HTTP servers in a Node.js application

Description

Non compliant code

package main

import (
	"github.com/gin-gonic/gin"
	"net/http"
)

func main() {
	r := gin.Default()

	r.GET("/file/:id", func(c *gin.Context) {
		fileID := c.Param("id")
		// Fetching the file based on the ID from the database without checking the user's permissions
		file := fetchFileFromDB(fileID)
		c.JSON(http.StatusOK, file)
	})

	r.Run() // listen and serve on 0.0.0.0:8080
}

func fetchFileFromDB(fileID string) *File {
	// Assume this function fetches the file from the database
	return &File{}
}

type File struct {
	ID   string
	Name string
	Data string
}

The code above is a simple implementation of a file fetching endpoint in a Go application using the Gin framework.

The vulnerability lies in the /file/:id endpoint. When a GET request is made to this endpoint with an ID parameter, the application fetches the file with that ID from the database and returns it without checking if the user making the request has the necessary permissions to access that file.

This is an example of an Insecure Direct Object Reference (IDOR) vulnerability, where an unauthorized user can access or manipulate information of other users just by knowing the identifier that differentiates them.

In this case, if an attacker knows or guesses the ID of a file, they can access that file without having the necessary permissions. This can lead to unauthorized access to sensitive information and potential data breaches.

Steps

• Implement an authentication and authorization system to validate user permissions before accessing files.
• Ensure that only authorized users can access and manipulate files by checking their permissions.
• Use a secure session management mechanism to track and validate user sessions.
• Implement proper access control mechanisms to restrict unauthorized access to files.
• Validate user input and sanitize file IDs to prevent any potential injection attacks.
• Implement proper error handling to handle unauthorized access attempts gracefully.
• Regularly update and patch the application and its dependencies to address any security vulnerabilities.

Compliant code

package main

import (
	"github.com/gin-gonic/gin"
	"net/http"
)

func main() {
	r := gin.Default()

	r.Use(AuthMiddleware()) // Use authentication middleware

	r.GET("/file/:id", func(c *gin.Context) {
		fileID := c.Param("id")
		user := c.MustGet("user").(User) // Get the authenticated user

		// Fetching the file based on the ID from the database and check the user's permissions
		file, err := fetchFileFromDB(fileID, user)
		if err != nil {
			c.JSON(http.StatusForbidden, gin.H{"error": "You don't have permission to access this file"})
			return
		}
		c.JSON(http.StatusOK, file)
	})

	r.Run() // listen and serve on 0.0.0.0:8080
}

func AuthMiddleware() gin.HandlerFunc {
	return func(c *gin.Context) {
		// Implement your authentication logic here
		// If authentication is successful, set the authenticated user in the context
		// c.Set("user", authenticatedUser)
	}
}

func fetchFileFromDB(fileID string, user User) (*File, error) {
	// Assume this function fetches the file from the database and checks the user's permissions
	return &File{}, nil
}

type File struct {
	ID   string
	Name string
	Data string
}

type User struct {
	ID string
}

The updated code includes an authentication middleware that is used to authenticate users before they can access any files. This middleware is applied to all routes by using the Use function on the router instance.

In the route handler for /file/:id, we now also fetch the authenticated user from the context. This user is then passed to the fetchFileFromDB function, which is assumed to check the user's permissions before fetching the file.

If the user does not have the necessary permissions to access the file, the fetchFileFromDB function should return an error. This error is then checked in the route handler, and if it exists, a 403 Forbidden response is returned to the client.

This way, we ensure that only authenticated and authorized users can access and manipulate files. We also handle any unauthorized access attempts gracefully by returning an appropriate HTTP status code and error message.

Please note that you need to implement the actual authentication logic in the AuthMiddleware function and the permission checking logic in the fetchFileFromDB function. The provided code is just a skeleton to guide you on how to structure your code to fix the insecure direct object reference vulnerability.

References

• 306.Insecure object reference - Files